1. Field of the Invention
The present invention generally relates to a method and apparatus for carburizing, quenching and tempering, and, more particularly, to a method for carburizing, quenching and tempering, by which a step of carburizing can be incorporated into a machining and manufacturing process to be performed by an on-line machining and manufacturing system as one stage thereof, and to an apparatus therefor.
2. Description of the Related Art
Hitherto, continuous gas carburize/quench furnaces of the tray pusher type or of the roller hearth type have been used as apparatuses for carburizing and quenching, so as to carry out the mass production of (steel) products. The continuous gas carburize/quench furnace of any of such types usually provides around-the-clock operation in what is called a heat-treating shop, which is away from a machining shop, by being made to be offline from a machining (process) apparatus. Further, the furnace has employed a producing method by which a heat treatment is performed according to a batch system that is adapted to set up a large number of workpieces (such as parts), which are to be processed, on trays, respectively.
Meanwhile, the process to be performed by such a conventional continuous gas carburize/quench furnace is composed of steps illustrated in FIG. 10.
Namely, the cutting of the workpieces are first performed in the machining shop. Subsequently, the cut workpiece is transported from the machining shop to the heat-treating shop which is made to be offline and is away therefrom. When the workpieces arrive at the heat-treating shop, the set-up step of setting up the workpiece on a tray is performed by jigs. After cleaning, the workpieces are loaded into the continuous gas carburize/quench furnace. Thence, the steps of carburizing and quenching are performed in the continuous gas carburize/quench furnace. Subsequently, the workpieces are cleaned and tempered. Upon completion of a sequence of heat-treating steps, a step of taking the workpiece out of the tray and further disassembling the workpiece is performed. The disassembled workpiece is transported to the machining shop which is made to be offline and is away from the heat-treating shop. Thereafter, in the marching shop, the grinding of the workpiece is performed.
The aforementioned process of FIG. 10, which is to be performed in the conventional continuous gas carburize/quench furnace, has the following problems.
i) Because the machining shop is placed apart from the heat-treating shop, a transport system and personnel therefor are needed. Moreover, it is necessary to stock workpieces, which are to be processed (or treated), for a time period having a predetermined length. PA1 ii) There is the necessity of the set-up step of setting a workpiece on a tray by using a jig so as to charge the workpiece into the furnace. Moreover, the disassembling step of taking out the workpiece, which has been set on the tray, therefrom is needed upon completion of the heat-treating step. PA1 iii) It takes time to raise and lower the temperature of the workpiece. The lead time of the heat treatment is long. Thus, the process from the step of inserting or charging the workpiece into the furnace to the step of extracting thereof from the furnace is time-consuming. PA1 iv) When starting up the furnace, it takes long time to perform seasoning for regulating (or controlling) the furnace atmosphere. PA1 v) Batch processing results in variation in quality among the heat-treated workpieces. PA1 Z.gtoreq.X/Y PA1 C.gtoreq.M/Y, H.gtoreq.N/Y PA1 Z.gtoreq.X/Y PA1 C.gtoreq.M/Y, H.gtoreq.N/Y PA1 W.gtoreq.L/Y
The present invention is accomplished to solve the aforementioned problems.
Accordingly, an object of the present invention is to provide a method for carburizing, quenching and tempering workpieces, by which the step of carburizing can be incorporated into a machining and manufacturing process to be performed by an on-line machining and manufacturing system as one stage thereof, and by which high-quality treatment or processing can be achieved without occurrences of variation in quality among heat-treated products.
Further, another object of the present invention is to provide an apparatus for such a method.